18 June 2015

Trans fats might interfere with memory

The FDA has released a determination that artificial trans fats are not 'generally recognized as safe'. Food manufacturers now have three years to remove partially hydrogenated oils from their products.

Artificial trans fats in processed foods, which were all but banned by the U.S. Food and Drug Administration (FDA) this week, may interfere with memory, according to a new study.

Not 'generally recognised as safe'

It's not clear if trans-unsaturated fatty acids, or trans fats, might interfere with memory by directly affecting the nervous system, or by contributing to overall cardiovascular disease, which harms the brain as well, researchers say.

Following a two-year public comment period, the FDA released a final determination that artificial trans fats in processed foods are not "generally recognized as safe". Food manufacturers now have three years to remove partially hydrogenated oils from their products.

This is good news, and an important step in the right direction, according to Dr. Beatrice Alexandra Golomb of the University of California, San Diego in La Jolla, lead author of the new study linking trans fats to poorer memory.

Trans fats occur in the milk and body fat of some animals, but the primary dietary source of trans fats is processed foods. The artificially produced oils extend food shelf life.

They had already been linked to poorer lipid profiles, including higher "bad" LDL cholesterol, worse metabolic function, insulin resistance, inflammation and poorer cardiac and general health before the new study investigated potential memory issues, Golomb and her coauthors write in PLoS One.

The researchers analysed data from a larger study of statin drugs. They focused on self-reported dietary patterns and the results of a word recall test performed with more than 600 adult men without diabetes, cardiovascular disease or dangerous cholesterol levels.

To test word recall, the men were shown a series of 104 cards with 82 unique words and 22 words repeated in the set, and were asked to identify the words they had seed earlier in the test.

Decreasing word recall

On average, the men correctly identified 85 of the words.

Among men under age 45, increasing dietary trans fatty acid consumption was associated with decreasing word recall, with each additional gram of trans fat per day matched to 0.76 fewer words identified correctly.

At the time of the study, participants' trans fat consumption ranged up to 28 grams a day, the researchers write. That would translate to 21 fewer correct word-recall responses out of an average normal score of 86.

"A lot of us are involved in jobs where words are important," Golomb told Reuters Health. A decrease of only a few words on this recall test can make a difference, she said, and it's reasonable to think that other areas of memory might also be associated with trans fats.

There was no association between trans fats and memory performance for people over age 45, which the study team says is in line with other research because older people have additional factors influencing memory.

As with any observational study, it is never completely possible to exclude other explanations, and the results do not indicate that trans fats cause changes in memory, Golomb noted.

"I think it's overstating the data in the conclusion that it's causal," said Dr. Jennifer G Robinson, director of the Prevention Intervention Centre at the University of Iowa in Iowa City, who was not part of the new study.

"We know that trans fat is bad for you," increasing the risk for heart attack, stroke and death, she told Reuters Health.

No good reasons to consume trans fat

But people who eat more processed foods may have other unhealthy habits that may explain memory performance, she said.

Looking for adverse cognitive effects, you would expect older people with more years of exposure to trans fats to have more memory problems, but that was not the case in this study, Robinson said.

"There are no good reasons to consume trans fat," said Dr. Alice Lichtenstein, director and senior scientist of the Cardiovascular Nutrition Laboratory at Tufts University in Medford, Massachusetts.

There has been a dramatic decrease in trans fatty acids in foods introduced in recent years but there are still some available, she told Reuters Health. People who eat very large amounts of trans fats may displace healthier fats from their diets, she noted.

The FDA estimates that trans fat consumption in the U.S. decreased by about 78 percent between 2003 and 2012, driven by manufacturers removing the fats from many foods and having to list them on nutrition labels.

But manufacturers are currently allowed to label any product with less than 0.5 grams of trans fats per serving as 0 grams of trans fats, Golomb said. Just because a product says "0 grams" doesn't mean it has no trans fats.

"Look for the words hydrogenated, shortening or margarine on the label," she said. Common sources are microwave popcorn, shelf-stable baked goods, non-dairy creamer and fast foods.

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